Usually previously, the intake air and the exhaust gases were introduced and removed from the end of a long tunnel underneath the checker brickwork of the regenerators along each side of a long hearth-type of furnace such as a glass furnace. The air and gases thus took any path of least resistance up or down through the checker brickwork which resulted in the uneven distribution of temperature throughout the brickwork producing hot and cold spots at different locations along the long regenerators. This, however, produced an uneven combustion and temperature along the furnace, as well as required additional amounts of fossil fuel to be injected into the air at the cooler spots to produce the desired heat in the furnace.
It is known to place vertical partitions at spaced intervals along the brickwork and/or to provide gates at either the top and/or bottom of the brickwork at the openings from the ducts to and from the brickwork as shown for example in Smythe U.S. Pat. No. 478,767 issued July 12, 1892 and McBurney U.S. Pat. No. 2,114,744 issued Apr. 19, 1938. Thus the tunnel under the checker brickwork of the regenerators could be considered in effect a manifold and the purposes of these gates were either to shut off a section for the replacement of its brickwork during operation of the rest of the regenerator, or to control the temperature of the regenerator as a whole. However, intake air and combustion gases both passed through the same tunnel and the same gates to and from these regenerators and the adjustment of the gates for distributing intake air usually is not the same as that required for the exhaust gases. Thus the most effective, efficient and uniform heating and cooling of the regenerators can not be obtained by the construction of the ducts to the checker brick regenerators known in the prior art, and the best and most economic use of the fossil fuels for firing these furnaces through such regenerators is not gained. Furthermore, if these prior art gates were used, the accumulation of batch carryover material thereon would require excessive maintenance and eventually would make these gates immovable.